Selenium is nutritionally essential for humans but is toxic at higher levels, with a narrow safe range of intake. Selenium-containing compounds are known to play an important role in protection against several diseases, including cancer.
From the late 1960s, a few observational studies reported that people with high levels of selenium in their diet or in their body tissues had lower risk of cancer, and some laboratory studies showed that selenium could inhibit the growth of cancer cells. This led to widespread interest in selenium supplements.
It was observed that people with higher levels or intake of selenium had lower frequencies of certain types of cancers such as lung, bladder and prostate cancer, but no difference for other types such as breast cancer.
Newly-published prospective studies on oesophageal, gastric-cardia and lung cancer have reinforced previous evidence, which is particularly strong for prostate cancer. Interventions with Se have shown benefit in reducing the risk of cancer incidence and mortality in all cancers combined, and specifically in liver, prostate, colo-rectal and lung cancers. The effect seems to be strongest in those individuals with the lowest Se status.
The World Cancer Research Fund found in 2007 that there was probable evidence that selenium and selenium supplements reduced the risk of prostate cancer, and limited suggestive evidence that they reduced the risk of lung and bowel. Selenium was also linked to a limited suggestive lower risk of stomach cancer, and selenium supplements to a limited suggestive increased risk of skin cancer.
Selenium and prevention of cancer
